Hardened-lead alloy and method of producing same



h Last (saw June 26, E928. 1,674,954

R. S. DEAN ET AL HARDENED LEAD ALLOY AND METHOD OF PRODUCING SAME Filed Feb. 5, 1924 & m W wry REGINALD SCOTT DEAN WILLIAM EWART HUDSON, OAK PARK, ILLINOIS, AS-

SIGNORS TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y.,

A CORPORATION NEW YORK.

HARDENED-LEAD ALLOY AND METHOD OF PRODUCING SAME.

Application filed February The principal object of this invention is to form a high lead content alloy having the desirable properties of lead, as for example, resistance to corrosion, plasticity, etc., but

5 with greater hardness. toughness, tensile strength, resistance to abrasion and related mechanical properties.

A further object of this invention is to provide a practical and commercial method for producing a lead alloy having the characteristics above noted.

This invention is based on the discovery that by adding to lead, matter which will be soluble in solid lead. and have a solubility which will vary with a change in temperature, the lead alloy can be treated by a proeess, which will be described hereinafter, to so enhance the above described properties of the alloy as to make it a radically different :0 material. It is well known that certain properties of lead may be improved by adding other elements. For instance it has been a common practice to addtinor antimony to lead for the purpose of hardening the :5 lead. While in practicing the process of this invention antimony or tin may be alloyed with lead as a step thereof, the other steps of the process are such that the resultant alloy has such a hardness, tensile l0 strength, toughness, etc., as to be in fact a. radically different material than any alloy containing the same ingredients heretofore produced. In actually working out the process antimony was used as the alloying metal because it is the metal usually employed for hardening lead, is inexpensive and easily obtainable. It is to be understood, however,

that other alloying matter may be employed I without departing from the spirit and scope to of the invention which is only to be limited by the scope of the appended claims.

' It has been the belief of metallurgists and others skilled in the art that antimonywas not soluble in lead in the solid state. Guertler, recognized as an authority in metallurgy, makes this statement in his Metallographie Bornstrager, 1912, Vol. 1, page 792, as does also Dessau, Physikalische Eigenshaften der Legierungen, Vieweg, 1912, p.

87: and Hoyt, Metallography, McGraw- Hill Book Co, 1921, p. 52. These and other equally well known authorities conclude,

5, 1924:. Serial No. 690,716.

and it has been generally accepted, that solid solutions are not formed, partlcularly in alloys rich in lead.

It has also been known that when leadantimony alloys were made having more than a- 1% antimony content, the alloys showed eutectic areas under the microscope, and investigations tended to show that the eutectic areas increased as the antimony'content was raised. By the use of the process hereinafter described, lead antimony alloys may be produced having a greater tensile strength and hardness than any lead-antimony" alloys heretofore-'made, and which at the same time are free from eutectic areas. In developing the process which is the basis of this application, discovery was made, through experiments, that antimony is soluble in lead at the eutectic temperature. Additional investigation revealed that the percentage of antimony in solid solution increases with increase in temperature, and

that the temperature of greatest solubility is around or slightly belowthe eutectic fusmg temperature.

Based on these discoveries the process for improving lead antimony alloys constituting the present invention, was developed, this process consisting briefly in combining the proper proportions of lead and antimony forming a solid solution thereof, reducing to a supersaturated solutiomand then allowing the alloy to assume a more stable state.

More specifically, the process consists in addingto lead a greater percentage of antimony than is soluble at room temperature, but not substantially more antimony than is soluble at a temperature slightly below the eutectic fusing temperature.- Thisresulting alloy is then heated at a temperature below or not appreciably greater than 240 C. until a substantially homogeneous solid solution is formed. The alloy is then quenched to a lower temperature and subsequently aged at a temperature around room temperature or slightly above. The proper length of time and temperature of the heating or solution forming step, quenching or supersaturating step, and aging step of the process,

wherein the alloy is allowed to assume a more stable state, together with the proper proportions of the lead and antimony will vary, depending upon the properties desired in the alloy and also depending upon the uses to which the alloy is to be put. In the drawings accompanying this-application: j

Fig. 1 is a curve showing solid solubility of antimony in lead.

Fig. 2 is a curve showing the increase in tensile strength in lead antimony alloys' treated according to this invention.

Fig. 3 is a curve showing the tensile strength of lead-antimony alloys not treated according to this invention.

It will readily be seen that several variables are to be dealt with and considered in determining the proper process for producing a particular product.

These variables are as follows:

Composition of the alloy.

. Size of the mass heated.

. Shape of the mass heated.

. Time of heating.

. Temperature of heating.

. Temperature from which quenched.

Temperature of quenching bath. Temperature during aging.

. Time of age treatment.

In order to assist those skilled in the art todetermine the proper characteristics "of the process to be employed to produce a de- 'sired product, each specific process necessarily embodying the fundamental features of the process constituting the present invention and defined above, each one of the variables will be taken up and discussed in relationship to the other variables.

/ 1. Composition; 6;- the alloy.

Experiments tend to show that the greatest improvement of a lead-antimony alloy treated by this heating-quenching-aging method is obtained in-an alloy made up of a percentage of antimony that is soluble in solid lead'at or slightly below the eutectic and the ture., The temperatures are calibrated on a the bottom line.

fusing temperature. Fig. '1. of the attached drawing is a graphic curve, showing approximately what the solid solubility is for pure lead antimony alloys.

In Fig. 1 the line A. B. represents the solid solubility of antiinony in lead, the point A indicating approximately the melting point point B, so called room temperathe left-hand margin, while the 'antimony content is indicated by the. calibrations on It will be seen that the percentage of antimony which at 20 C. or about room temperature is soluble in lead is about one per cent. "(1%.) The solu bility increases gradually up to about 200 C. where the solubility is about 1.4%, and then showsv a marked increase up to its maximum, about 2.25% at the point A or about 245 C. This is about the eutectic fusing temperature, and thep'oint' of greatest solid than that amount tensile strength. I p g Y Fig. 3 of the drawing shows the increase solubility at a point between A, and the dotted line. Between the dotted line at C and-the solid line at A the eutectic fuses,

and the alloy begins to assume a liquidstate. Above the solid line at A the alloy is in the form of a liquid.

In lead-antimony alloys the tensile strength possible with varying content of antimony is indicated by the graphic curve in Fig. 2 of 'the attached drawlng. The antimony content is shown on the lower line,

while the increase in tensile strength over the untreated alloy is shown on the lefthand margin. As the curve indicates thegreatest tensile strength is secured using about 2.25% of antimony,- while more or less gives correspondingly less in tensile strength obtained in lead by the addition of; antimony not treated by the processof this invention. The tensile strength 1 obtained by adding 2.25% of antimony is slightly over 4,00011bs. per square inch. Since Fig. 2 shows an increase of 7,000 lbs. per square inch, the addition of these'two figures will give slightlyabove 11,000 lbs.-,'

which is the tensile strength of the treated 2.25% antimony lead alloy. A 2.25% ,antimony lead alloy treated by the method herein dsecribed, has approximately three times the tensile strength of the untreated alloy.

A 2.25% antimony lead alloy untreated shows a mic'ro-Brinell hardness of 8, while the same alloy treated according to this heating-quenching-aging method. showsa micro-'Brinell hardness of 28. A tensile strength analysis of the lead antimony sys tem shows that in alloys not treated by theprocess of this invention the greatest tensile strength is obtained in an alloy of 10% antimony and 90% lead. This alloy has a tensilev strength not greater than 8,000 lbs.

per square inch and a micro-Brinell hardness Tof 17.

I? and 3. Size anti shape ofmass heated.

. The size andshape of the alloy mass willv determine to'some extent thetime of heating or soaking -required.' The explanation of ins Y this fact will appear from subsequent portions of this specification. It is enough to state here, that in general, a larger mass will require considerably more heating than a small mass, and that the vertical increase in the shape of any mass will result as well,

in necessitating longer heat treatment: to accomplish the same result. I

I .4. of heating.

1 Although the percentage of antimony soluble in lead at a. given temperature ma be said to be acerta'in amount (for instance a but 2.25% at 240 0.), some time must be aliao lowed to permit the formation of the solution with the ratio of lead and antimony desired. The alloy mass to be treated should be heated for a period of time to effect the formation of a perfect homogeneous solid solution. If the molecular formation of the] given mass of alloy is such as to favor quick solution, the time is not so great. If during cooling, or at any time, the molecular constituents are widely separated through crystallization, due to gravitational action of the lighter antimony rising to the top of the casting, the formation of a homogeneous solution during heating is slower, and the heating must be continued for a comparatively greater length of time. Seventy-two hours heating seems to give uniformly good results for lead antimony alloys of 2.25%

antimony content, or 'less.

5. Temperature of heating.

The temperature that is required during the heating step of the process will vary with the percentage of antimony present. Curve A, Fig. 1, shows the temperature that would 'be required for any given antimony content within the solubility range. It is to be noted, however, that the temperature of heating must be high enough to permit the antimony present to enter solution. If a lower temperature is employed, less improvement is obtained.

In actual practice, if the maximum improvement with the percentage of antimony present is desired, good results are obtainable by heating at 240 (1., because this temperature is not too high to be dangerously close to melting, but is high enough to allow substantially the maximum amount of antimony to enter into solution. A temperature of 240 C. is higher than is required for some lead-antimony alloys, but the use of a higher temperature than is actually required provided the fusing'temperature is not exceeded, does not seem to cause any injurious results, Heating at a higher temperature, providing the temperature is below the fusing point tends to hasten the formation of a solid-solution. The time of heating can therefore sometimes be cut down by employlng a higher temperature than is actually required for forming the solid solution.

6. Temperature of quenching.

in substantially the same condition, temporarily of course, as it was in the hot state,

and to prevent the crystal growth which would be incident with slow cooling.

Water at room temperature is found. to

- ture of lead '7. Temperature from which quenched. v

Ordinarily quenching should take place from about the same temperature as that at which the alloy has been heated. But an alloy article may be heated at whatever temperature is required to form a homogeneous solid solution, allowed to cool slowly down to a lower temperature, and then quenched from the lower temperature. Less hardening seems to be obtained, however, than when the alloy mass is quenched from the higher temperature, but other qualities are developed, such as greater elongation. Where hardening can be sacrificed to this'species of toughness, the lowering of the temperature before quenching may be employed.

8 and .9. and temperature of aging.

Aging may take place at any temperature below the temperature of appreciable crystal growth of the components of the alloy,- believed for lead antimony alloys of the type susceptible to greatest improvement to be about 100 G. In general the lower the temperature below that point, the slower the improvement. At temperatures below 0 C. the improvement takes place slowly.

In practice a good temperature is found to be any temperature around room temperature. An alloy of 2.25% antimony and lead was found to harden in 72 hours at room temperature, its tensile strength being about 11,500 lbs. per square inch at the end of that time.

The variable requirements of time and temperature of heating may be further I changed by'a mechanical process directed on or against the alloy either before, after, or during heating.

The time of heating may be cut down by the use of any mechanical means which will tend to hasten the formation of the solid solution. Pieces of alloy that are subjected to sufficient pressure to deform the structure of the mass require less heating. Rolled or formed articles form solid solutions when heated, in a short, time, sometimes a matter of minutes, while cast ingots and the like, unless pounded, submitted to pressure or acted upon in some similar mechanical manner, will frequently require as 'much' as 72 hours or even more.

' Lead alloys treated according to this process'may be used for a variety of purposes. They can be used wherever certain qualities of the lead are required, with added tensile stren th and hardness. For example, they may e used to advantage in the manufacsheath for cables, lead pipe, storage battery plates, lead tape and the like.

v places w They may be used in place of the .antimony, and

the invention is present in any process for hardening lead which consists in addingJzo lead a solute and then subjecting the resulting alloyto a treatment of which the forming of a substantially supersaturated solid so ution .is a step.

What is claimed is:

1. A method for making an improved lead alloy, which consists in alloying antimony with lead, reducing the resulting alloy to a with lead, forming the resulting alloy into a saturated solution, and causing said alloy toassume a more stable state.

and causing said alloy to assume a more alloy,

' lead-antimony alloy, ing the alloy at a alloy,

lead alloy,

supersaturated solid solution, and causing said alloy to assume a more stable state.

2. A method for making an improved lead alloy, which consists in alloying antimony solid solution, reducing said alloy to a super- 3. A process for making an improved lead which consists in alloying antimony with lead, subjecting said alloy to heat treatment to reduce it to a supersaturated solid solution, substantially all of the antimony being in said supersaturated solid solution,

stable state.

4. A process for making an improved lead with lead, heating the alloy until a solid solution is formed, substantiallyall of the antimoriy being in said solid solution, quenching said alloy and then aging it.

' 5. A process for producing an improved which consists in alloying antimony with lead, heating the resulting alloy below the fusion temperature until a solid solution is formed, substantially all, of the antimony being in said solid solution, quenching said alloy, and aging.

6. process-for making'an improved leadantimony alloy, which consists in heating the alloy at a temperature high enough and for .a period of time suflic'rent'toallow theantimony present to enter solid solution, subsolid solution, quenching, and aging.

7. A method for makingan improved which consists in heat temperatureof 2409 U. f untll a solid solution. is formed, substantially 4 all of the antimony being in saidsolid solution, quenching, and aging.

8. A method for producing an improved lead-antimony alloy, which consists heat- .being in said solid solution, the temperature at which it is heated, and

q lead-antimony alloy,

which consists in alloyingantimony 16. A process for ature-to' room temperature,

ing the alloy at a temperature at which solid solution is formed until a solid solution results, substantially all of the antimony being in said solid solution, quenching from that temperature, and aging.

9. A process for producing an improved lead-antimony alloy, which consists in heating the alloy at a temperature of 240 0. until a solid solution is formed, substantially all of the antimony'being in said solid solution, quenching from that temperature, and aging.

10. A process lead-antimony alloy, which consists in heating the alloy at a temperature below the fusion temperature until a solid solution is formed, substantially all of the antimony quenching from aging;

'11. A process for producing an improved which consists in heating the alloy until solid solution is formed,

substantially all 'ofthe antimony being in said solid solution, quenching from the same temperature to room temperature, and

aging. a

12. A process for producing an improved lead-antimony alloy, which consists in heat ing the alloyat a temperature below the for producing an improved fusion temperature until a solid solution is formed, substantially room'temperature, and aging.

13. A process for producing an improved lead-antimony. alloy, which consists in heating the alloy at a temperature below the fusion temperature until a solid solution is formed, substantially all of the antimony being in said solid solution, a temperature below 0., and aging.

14. A process for producing an improved lead-antimony alloy, which consists inheating the alloy at a temperature slightly below the fusion temperature until a solid solution is 7 formed, substantially .all of the antimony being in said solid solution, quenching to a temperature below 100 (1., and aging. 7

15. A process f r producing an improved lead-antimony alloy, which consists in heatuntil a solid solution is formed, substantially all of the antimony being in said solid solution, quenching to a temperature below 100 stantially all of the antimony being in said C i and aging producing an improved lead-antimony alloy, which consists in heating the alloy ata temperature of "240 C. until a solid solution is formed, substantiallyall of the antimony being in said solid solution, quenching from that same temperand aging.

all of .the antimonybemg in said solid solution, quenching to- 17 A process -for producing an improved v lead-antimony alloy, which consists in heating the alloy at a temperature of 240 C.

lead-antimony alloy,

1 ing in said until a solid solution is formed, substantially all of-the antimony being in said solid solution, quenching from that same temperature to a temperature below 100 0., and aging.

18. A process for producing an improve lead-antimony alloy, which consists in heating the alloy at a temperature below the fusion temperature until a solid solution is for-med, substantially all of the antimony being in said solid solution, quenching said alloy, and aging said alloy at room temperature.

1.9. A process for producing an improved which consists in heat-' ing the alloy at a temperature slightly below the fusion temperature until a solid solution is formed, substantially all of the antimony being in said solid solution, quenching the alloy to room temperature, and aging at room temperature.

20. A process for producing an improved lead-antimony alloy, which consists in heating the alloy at a temperature below the fusion temperature until a solid solution is formed, substantially all of the antimony besolid solution, quenching, and aging at a temperature below 100 C.

21. A process for producing an improved lead antimony alloy, which consists in heating the alloy at a temperature below the fusion temperature until a solid solutionis formed, substantially all of the antimony being in said solid solution, quenching to a temperature below 100 0., and aging at room temperature.

22. A process for producing an improved lead-antimony alloy, which consists in heating the alloy at a temperature slightly below the fusion temperature until a solid solution is formed, substantially all of the antimony being in said solid solution, quenching to a temperature below 100 0., and aging at a temperature below 100 C.

23. A process for producing an improved lead-antimony alloy, which consists in heating the alloy at a temperature of 240 0. until solid solution is formed, substantially all of the antimony being in said solid solution, quenching said alloy from 240 C. to a temperature not greater than 100 (3., and aging said alloy after quenching at a temperature not greater than 100 C.

24. A process for producing an improved alloy, the major constituent of which is lead,

which consists in alloying with leadsubstamtially the greatest amount of antimony which will form a solid solution therewith at any temperature,

ity

properties of lead, which consists in alloyheating the resulting alloy at the temperature of greatest solidsolubilof the solute material until a substan-' tially homogeneous solid solution is formed,

ing with lead substantially the greatest amount of antimony which will go into solid solution in lead at any temperature, heating the resulting alloy in a single step at the temperature of maximum solubility until a. d substantially homogeneous solid solution is formed, quenching to room temperature, and then aging at a temperature lower than the temperature of maximum solubility.

26. A method for obtaining improvement in the properties of lead, consisting in alloying with lead substantially the greatest amount of antimony which is soluble in lead at any temperature at which the resulting alloy is a solid, heating the resulting alloy at the temperature of maximum solubility until a substantially homogeneous solid solution is formed, then so treating said solid solution as to hold it in substantially the same condition at a lower temperature, and aging at a temperature below the temperature of maximum solubility.

27. A method for improving the properties of lead, consisting in alloying with lead substantially the greatest amount of antimony which will go into solution in lead at any temperature at which the resulting alloy is a solid, heating the resulting alloy until a substantially homogeneous solid solution is formed, quenching the alloy, and then aging at a temperature lower than that employed to produce the solid solution.

28. A method for improving the properties of lead, consisting in alloying with lead substantially the greatest amount of antimony which will go the temperature at which an eutectic of the two materials fuses, heating the resulting alloy at a temperature slightly below the eutectic temperature until a substantially homogeneous solid solution is formed, quenching, and aging at a temperature lower than that employed for producing the solid solution.

29. A method for producing an improved alloy, the major. constituent of which is lead, which consists in alloying with lead a larger quantity of antimony than is soluble in lead at room temperature, heating the resulting alloy until a substantially homogeneous solid solution is formed, quenching, and aging at a temperature intermediate the temperature of maximum solubility -and room temperature.

1 30. A method for producing an improved.

ble in solid lead at room temperature, reduc ing the resulting alloy to a supersaturated solld solution, and aging.

31.. A method for producing an improved alloy, the ma or constituent of which is lead, whichconsists in alloying with lead I a larger quantity of antimony than .issoluinto solution in lead at we I ble insolid lead at room temperature, heating the resulting alloy until a solid solution is formed, substantially all of the antimony being in said solid solution, quenching, and aging.

1132. A process for producing an improved a o lead? which consists in alloying with lead substantially the greatest amount of antimony which will form a solid solution therewith at any temperature, heating the resulting alloy until a substantially homogeneous solid solution is formed, quenching, and aging.

33. A process for producing an improved alloy, the major constituent of which is i lead, which consistsin alloying with lead resultinfg substantially the greatest amount of antimony which willyform a solid solution therewith at any temperature, heating the alloy at-the temperature of greatest soli solubilityof antimony until a substantially homogeneous solid solution is formed, quenching the resulting alloy to produce a supersaturated solid solution, and agin the alloy-at a temperature intermediate t l le temperature of maximum solubility of antimony and room temperature.

the major constituent of which isthe resulting 34. A method for lead, which consists in alloying with lead a quantity of antimony larger than that which is soluble in solid lead at room temperature and less than that which is soluble in solid lead at the fusion temperature of the alloy, reducing the resulting alloy to a supersaturated solid solution, and aging.

35. A process for producing an improved alloy, which consists in alloying with lead not less than 1% and not more than 2.5% antimony, reducing the resulting alloy to a supersaturated solid solution, and aging.

36. A. process for producing an improved alloy, which consists in alloying approximately 2.45% antimony with lead, heating alloy at a temperature of about 240 C. until a substantially homogeneous solid solution is formed, the alloy to produce a supersaturatedsolid solution, and aging the quenched alloy at room temperature.

In witness whereof, we hereunto subscribe our names this 22nd day of January A. D.,

REGINALD SCOTT DEAN. WILLIAM EWARTHUDSON.

quenching producing an improved alloy, the major constituent of which is 30 

